1 // SPDX-License-Identifier: GPL-2.0 2 #include <linux/pagewalk.h> 3 #include <linux/highmem.h> 4 #include <linux/sched.h> 5 #include <linux/hugetlb.h> 6 #include <linux/mmu_context.h> 7 #include <linux/swap.h> 8 #include <linux/leafops.h> 9 10 #include <asm/tlbflush.h> 11 12 #include "internal.h" 13 14 /* 15 * We want to know the real level where a entry is located ignoring any 16 * folding of levels which may be happening. For example if p4d is folded then 17 * a missing entry found at level 1 (p4d) is actually at level 0 (pgd). 18 */ 19 static int real_depth(int depth) 20 { 21 if (depth == 3 && PTRS_PER_PMD == 1) 22 depth = 2; 23 if (depth == 2 && PTRS_PER_PUD == 1) 24 depth = 1; 25 if (depth == 1 && PTRS_PER_P4D == 1) 26 depth = 0; 27 return depth; 28 } 29 30 static int walk_pte_range_inner(pte_t *pte, unsigned long addr, 31 unsigned long end, struct mm_walk *walk) 32 { 33 const struct mm_walk_ops *ops = walk->ops; 34 int err = 0; 35 36 for (;;) { 37 if (ops->install_pte && pte_none(ptep_get(pte))) { 38 pte_t new_pte; 39 40 err = ops->install_pte(addr, addr + PAGE_SIZE, &new_pte, 41 walk); 42 if (err) 43 break; 44 45 set_pte_at(walk->mm, addr, pte, new_pte); 46 /* Non-present before, so for arches that need it. */ 47 if (!WARN_ON_ONCE(walk->no_vma)) 48 update_mmu_cache(walk->vma, addr, pte); 49 } else { 50 err = ops->pte_entry(pte, addr, addr + PAGE_SIZE, walk); 51 if (err) 52 break; 53 } 54 if (addr >= end - PAGE_SIZE) 55 break; 56 addr += PAGE_SIZE; 57 pte++; 58 } 59 return err; 60 } 61 62 static int walk_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, 63 struct mm_walk *walk) 64 { 65 pte_t *pte; 66 int err = 0; 67 spinlock_t *ptl; 68 69 if (walk->no_vma) { 70 /* 71 * pte_offset_map() might apply user-specific validation. 72 * Indeed, on x86_64 the pmd entries set up by init_espfix_ap() 73 * fit its pmd_bad() check (_PAGE_NX set and _PAGE_RW clear), 74 * and CONFIG_EFI_PGT_DUMP efi_mm goes so far as to walk them. 75 */ 76 if (walk->mm == &init_mm || addr >= TASK_SIZE) 77 pte = pte_offset_kernel(pmd, addr); 78 else 79 pte = pte_offset_map(pmd, addr); 80 if (pte) { 81 err = walk_pte_range_inner(pte, addr, end, walk); 82 if (walk->mm != &init_mm && addr < TASK_SIZE) 83 pte_unmap(pte); 84 } 85 } else { 86 pte = pte_offset_map_lock(walk->mm, pmd, addr, &ptl); 87 if (pte) { 88 err = walk_pte_range_inner(pte, addr, end, walk); 89 pte_unmap_unlock(pte, ptl); 90 } 91 } 92 if (!pte) 93 walk->action = ACTION_AGAIN; 94 return err; 95 } 96 97 static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end, 98 struct mm_walk *walk) 99 { 100 pmd_t *pmd; 101 unsigned long next; 102 const struct mm_walk_ops *ops = walk->ops; 103 bool has_handler = ops->pte_entry; 104 bool has_install = ops->install_pte; 105 int err = 0; 106 int depth = real_depth(3); 107 108 pmd = pmd_offset(pud, addr); 109 do { 110 again: 111 next = pmd_addr_end(addr, end); 112 if (pmd_none(*pmd)) { 113 if (has_install) 114 err = __pte_alloc(walk->mm, pmd); 115 else if (ops->pte_hole) 116 err = ops->pte_hole(addr, next, depth, walk); 117 if (err) 118 break; 119 if (!has_install) 120 continue; 121 } 122 123 walk->action = ACTION_SUBTREE; 124 125 /* 126 * This implies that each ->pmd_entry() handler 127 * needs to know about pmd_trans_huge() pmds 128 */ 129 if (ops->pmd_entry) 130 err = ops->pmd_entry(pmd, addr, next, walk); 131 if (err) 132 break; 133 134 if (walk->action == ACTION_AGAIN) 135 goto again; 136 if (walk->action == ACTION_CONTINUE) 137 continue; 138 139 if (!has_handler) { /* No handlers for lower page tables. */ 140 if (!has_install) 141 continue; /* Nothing to do. */ 142 /* 143 * We are ONLY installing, so avoid unnecessarily 144 * splitting a present huge page. 145 */ 146 if (pmd_present(*pmd) && pmd_trans_huge(*pmd)) 147 continue; 148 } 149 150 if (walk->vma) 151 split_huge_pmd(walk->vma, pmd, addr); 152 else if (pmd_leaf(*pmd) || !pmd_present(*pmd)) 153 continue; /* Nothing to do. */ 154 155 err = walk_pte_range(pmd, addr, next, walk); 156 if (err) 157 break; 158 159 if (walk->action == ACTION_AGAIN) 160 goto again; 161 162 } while (pmd++, addr = next, addr != end); 163 164 return err; 165 } 166 167 static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end, 168 struct mm_walk *walk) 169 { 170 pud_t *pud; 171 unsigned long next; 172 const struct mm_walk_ops *ops = walk->ops; 173 bool has_handler = ops->pmd_entry || ops->pte_entry; 174 bool has_install = ops->install_pte; 175 int err = 0; 176 int depth = real_depth(2); 177 178 pud = pud_offset(p4d, addr); 179 do { 180 again: 181 next = pud_addr_end(addr, end); 182 if (pud_none(*pud)) { 183 if (has_install) 184 err = __pmd_alloc(walk->mm, pud, addr); 185 else if (ops->pte_hole) 186 err = ops->pte_hole(addr, next, depth, walk); 187 if (err) 188 break; 189 if (!has_install) 190 continue; 191 } 192 193 walk->action = ACTION_SUBTREE; 194 195 if (ops->pud_entry) 196 err = ops->pud_entry(pud, addr, next, walk); 197 if (err) 198 break; 199 200 if (walk->action == ACTION_AGAIN) 201 goto again; 202 if (walk->action == ACTION_CONTINUE) 203 continue; 204 205 if (!has_handler) { /* No handlers for lower page tables. */ 206 if (!has_install) 207 continue; /* Nothing to do. */ 208 /* 209 * We are ONLY installing, so avoid unnecessarily 210 * splitting a present huge page. 211 */ 212 if (pud_present(*pud) && pud_trans_huge(*pud)) 213 continue; 214 } 215 216 if (walk->vma) 217 split_huge_pud(walk->vma, pud, addr); 218 else if (pud_leaf(*pud) || !pud_present(*pud)) 219 continue; /* Nothing to do. */ 220 221 if (pud_none(*pud)) 222 goto again; 223 224 err = walk_pmd_range(pud, addr, next, walk); 225 if (err) 226 break; 227 } while (pud++, addr = next, addr != end); 228 229 return err; 230 } 231 232 static int walk_p4d_range(pgd_t *pgd, unsigned long addr, unsigned long end, 233 struct mm_walk *walk) 234 { 235 p4d_t *p4d; 236 unsigned long next; 237 const struct mm_walk_ops *ops = walk->ops; 238 bool has_handler = ops->pud_entry || ops->pmd_entry || ops->pte_entry; 239 bool has_install = ops->install_pte; 240 int err = 0; 241 int depth = real_depth(1); 242 243 p4d = p4d_offset(pgd, addr); 244 do { 245 next = p4d_addr_end(addr, end); 246 if (p4d_none_or_clear_bad(p4d)) { 247 if (has_install) 248 err = __pud_alloc(walk->mm, p4d, addr); 249 else if (ops->pte_hole) 250 err = ops->pte_hole(addr, next, depth, walk); 251 if (err) 252 break; 253 if (!has_install) 254 continue; 255 } 256 if (ops->p4d_entry) { 257 err = ops->p4d_entry(p4d, addr, next, walk); 258 if (err) 259 break; 260 } 261 if (has_handler || has_install) 262 err = walk_pud_range(p4d, addr, next, walk); 263 if (err) 264 break; 265 } while (p4d++, addr = next, addr != end); 266 267 return err; 268 } 269 270 static int walk_pgd_range(unsigned long addr, unsigned long end, 271 struct mm_walk *walk) 272 { 273 pgd_t *pgd; 274 unsigned long next; 275 const struct mm_walk_ops *ops = walk->ops; 276 bool has_handler = ops->p4d_entry || ops->pud_entry || ops->pmd_entry || 277 ops->pte_entry; 278 bool has_install = ops->install_pte; 279 int err = 0; 280 281 if (walk->pgd) 282 pgd = walk->pgd + pgd_index(addr); 283 else 284 pgd = pgd_offset(walk->mm, addr); 285 do { 286 next = pgd_addr_end(addr, end); 287 if (pgd_none_or_clear_bad(pgd)) { 288 if (has_install) 289 err = __p4d_alloc(walk->mm, pgd, addr); 290 else if (ops->pte_hole) 291 err = ops->pte_hole(addr, next, 0, walk); 292 if (err) 293 break; 294 if (!has_install) 295 continue; 296 } 297 if (ops->pgd_entry) { 298 err = ops->pgd_entry(pgd, addr, next, walk); 299 if (err) 300 break; 301 } 302 if (has_handler || has_install) 303 err = walk_p4d_range(pgd, addr, next, walk); 304 if (err) 305 break; 306 } while (pgd++, addr = next, addr != end); 307 308 return err; 309 } 310 311 #ifdef CONFIG_HUGETLB_PAGE 312 static unsigned long hugetlb_entry_end(struct hstate *h, unsigned long addr, 313 unsigned long end) 314 { 315 unsigned long boundary = (addr & huge_page_mask(h)) + huge_page_size(h); 316 317 return min(boundary, end); 318 } 319 320 static int walk_hugetlb_range(unsigned long addr, unsigned long end, 321 struct mm_walk *walk) 322 { 323 struct vm_area_struct *vma = walk->vma; 324 struct hstate *h = hstate_vma(vma); 325 unsigned long next; 326 unsigned long hmask = huge_page_mask(h); 327 unsigned long sz = huge_page_size(h); 328 pte_t *pte; 329 const struct mm_walk_ops *ops = walk->ops; 330 int err = 0; 331 332 hugetlb_vma_lock_read(vma); 333 do { 334 next = hugetlb_entry_end(h, addr, end); 335 pte = hugetlb_walk(vma, addr & hmask, sz); 336 if (pte) 337 err = ops->hugetlb_entry(pte, hmask, addr, next, walk); 338 else if (ops->pte_hole) 339 err = ops->pte_hole(addr, next, -1, walk); 340 if (err) 341 break; 342 } while (addr = next, addr != end); 343 hugetlb_vma_unlock_read(vma); 344 345 return err; 346 } 347 348 #else /* CONFIG_HUGETLB_PAGE */ 349 static int walk_hugetlb_range(unsigned long addr, unsigned long end, 350 struct mm_walk *walk) 351 { 352 return 0; 353 } 354 355 #endif /* CONFIG_HUGETLB_PAGE */ 356 357 /* 358 * Decide whether we really walk over the current vma on [@start, @end) 359 * or skip it via the returned value. Return 0 if we do walk over the 360 * current vma, and return 1 if we skip the vma. Negative values means 361 * error, where we abort the current walk. 362 */ 363 static int walk_page_test(unsigned long start, unsigned long end, 364 struct mm_walk *walk) 365 { 366 struct vm_area_struct *vma = walk->vma; 367 const struct mm_walk_ops *ops = walk->ops; 368 369 if (ops->test_walk) 370 return ops->test_walk(start, end, walk); 371 372 /* 373 * vma(VM_PFNMAP) doesn't have any valid struct pages behind VM_PFNMAP 374 * range, so we don't walk over it as we do for normal vmas. However, 375 * Some callers are interested in handling hole range and they don't 376 * want to just ignore any single address range. Such users certainly 377 * define their ->pte_hole() callbacks, so let's delegate them to handle 378 * vma(VM_PFNMAP). 379 */ 380 if (vma->vm_flags & VM_PFNMAP) { 381 int err = 1; 382 if (ops->pte_hole) 383 err = ops->pte_hole(start, end, -1, walk); 384 return err ? err : 1; 385 } 386 return 0; 387 } 388 389 static int __walk_page_range(unsigned long start, unsigned long end, 390 struct mm_walk *walk) 391 { 392 int err = 0; 393 struct vm_area_struct *vma = walk->vma; 394 const struct mm_walk_ops *ops = walk->ops; 395 bool is_hugetlb = is_vm_hugetlb_page(vma); 396 397 /* We do not support hugetlb PTE installation. */ 398 if (ops->install_pte && is_hugetlb) 399 return -EINVAL; 400 401 if (ops->pre_vma) { 402 err = ops->pre_vma(start, end, walk); 403 if (err) 404 return err; 405 } 406 407 if (is_hugetlb) { 408 if (ops->hugetlb_entry) 409 err = walk_hugetlb_range(start, end, walk); 410 } else 411 err = walk_pgd_range(start, end, walk); 412 413 if (ops->post_vma) 414 ops->post_vma(walk); 415 416 return err; 417 } 418 419 static inline void process_mm_walk_lock(struct mm_struct *mm, 420 enum page_walk_lock walk_lock) 421 { 422 if (walk_lock == PGWALK_RDLOCK) 423 mmap_assert_locked(mm); 424 else if (walk_lock != PGWALK_VMA_RDLOCK_VERIFY) 425 mmap_assert_write_locked(mm); 426 } 427 428 static inline void process_vma_walk_lock(struct vm_area_struct *vma, 429 enum page_walk_lock walk_lock) 430 { 431 #ifdef CONFIG_PER_VMA_LOCK 432 switch (walk_lock) { 433 case PGWALK_WRLOCK: 434 vma_start_write(vma); 435 break; 436 case PGWALK_WRLOCK_VERIFY: 437 vma_assert_write_locked(vma); 438 break; 439 case PGWALK_VMA_RDLOCK_VERIFY: 440 vma_assert_locked(vma); 441 break; 442 case PGWALK_RDLOCK: 443 /* PGWALK_RDLOCK is handled by process_mm_walk_lock */ 444 break; 445 } 446 #endif 447 } 448 449 /* 450 * See the comment for walk_page_range(), this performs the heavy lifting of the 451 * operation, only sets no restrictions on how the walk proceeds. 452 * 453 * We usually restrict the ability to install PTEs, but this functionality is 454 * available to internal memory management code and provided in mm/internal.h. 455 */ 456 int walk_page_range_mm_unsafe(struct mm_struct *mm, unsigned long start, 457 unsigned long end, const struct mm_walk_ops *ops, 458 void *private) 459 { 460 int err = 0; 461 unsigned long next; 462 struct vm_area_struct *vma; 463 struct mm_walk walk = { 464 .ops = ops, 465 .mm = mm, 466 .private = private, 467 }; 468 469 if (start >= end) 470 return -EINVAL; 471 472 if (!walk.mm) 473 return -EINVAL; 474 475 process_mm_walk_lock(walk.mm, ops->walk_lock); 476 477 vma = find_vma(walk.mm, start); 478 do { 479 if (!vma) { /* after the last vma */ 480 walk.vma = NULL; 481 next = end; 482 if (ops->pte_hole) 483 err = ops->pte_hole(start, next, -1, &walk); 484 } else if (start < vma->vm_start) { /* outside vma */ 485 walk.vma = NULL; 486 next = min(end, vma->vm_start); 487 if (ops->pte_hole) 488 err = ops->pte_hole(start, next, -1, &walk); 489 } else { /* inside vma */ 490 process_vma_walk_lock(vma, ops->walk_lock); 491 walk.vma = vma; 492 next = min(end, vma->vm_end); 493 vma = find_vma(mm, vma->vm_end); 494 495 err = walk_page_test(start, next, &walk); 496 if (err > 0) { 497 /* 498 * positive return values are purely for 499 * controlling the pagewalk, so should never 500 * be passed to the callers. 501 */ 502 err = 0; 503 continue; 504 } 505 if (err < 0) 506 break; 507 err = __walk_page_range(start, next, &walk); 508 } 509 if (err) 510 break; 511 } while (start = next, start < end); 512 return err; 513 } 514 515 /* 516 * Determine if the walk operations specified are permitted to be used for a 517 * page table walk. 518 * 519 * This check is performed on all functions which are parameterised by walk 520 * operations and exposed in include/linux/pagewalk.h. 521 * 522 * Internal memory management code can use *_unsafe() functions to be able to 523 * use all page walking operations. 524 */ 525 static bool check_ops_safe(const struct mm_walk_ops *ops) 526 { 527 /* 528 * The installation of PTEs is solely under the control of memory 529 * management logic and subject to many subtle locking, security and 530 * cache considerations so we cannot permit other users to do so, and 531 * certainly not for exported symbols. 532 */ 533 if (ops->install_pte) 534 return false; 535 536 return true; 537 } 538 539 /** 540 * walk_page_range - walk page table with caller specific callbacks 541 * @mm: mm_struct representing the target process of page table walk 542 * @start: start address of the virtual address range 543 * @end: end address of the virtual address range 544 * @ops: operation to call during the walk 545 * @private: private data for callbacks' usage 546 * 547 * Recursively walk the page table tree of the process represented by @mm 548 * within the virtual address range [@start, @end). During walking, we can do 549 * some caller-specific works for each entry, by setting up pmd_entry(), 550 * pte_entry(), and/or hugetlb_entry(). If you don't set up for some of these 551 * callbacks, the associated entries/pages are just ignored. 552 * The return values of these callbacks are commonly defined like below: 553 * 554 * - 0 : succeeded to handle the current entry, and if you don't reach the 555 * end address yet, continue to walk. 556 * - >0 : succeeded to handle the current entry, and return to the caller 557 * with caller specific value. 558 * - <0 : failed to handle the current entry, and return to the caller 559 * with error code. 560 * 561 * Before starting to walk page table, some callers want to check whether 562 * they really want to walk over the current vma, typically by checking 563 * its vm_flags. walk_page_test() and @ops->test_walk() are used for this 564 * purpose. 565 * 566 * If operations need to be staged before and committed after a vma is walked, 567 * there are two callbacks, pre_vma() and post_vma(). Note that post_vma(), 568 * since it is intended to handle commit-type operations, can't return any 569 * errors. 570 * 571 * struct mm_walk keeps current values of some common data like vma and pmd, 572 * which are useful for the access from callbacks. If you want to pass some 573 * caller-specific data to callbacks, @private should be helpful. 574 * 575 * Locking: 576 * Callers of walk_page_range() and walk_page_vma() should hold @mm->mmap_lock, 577 * because these function traverse vma list and/or access to vma's data. 578 */ 579 int walk_page_range(struct mm_struct *mm, unsigned long start, 580 unsigned long end, const struct mm_walk_ops *ops, 581 void *private) 582 { 583 if (!check_ops_safe(ops)) 584 return -EINVAL; 585 586 return walk_page_range_mm_unsafe(mm, start, end, ops, private); 587 } 588 589 /** 590 * walk_kernel_page_table_range - walk a range of kernel pagetables. 591 * @start: start address of the virtual address range 592 * @end: end address of the virtual address range 593 * @ops: operation to call during the walk 594 * @pgd: pgd to walk if different from mm->pgd 595 * @private: private data for callbacks' usage 596 * 597 * Similar to walk_page_range() but can walk any page tables even if they are 598 * not backed by VMAs. Because 'unusual' entries may be walked this function 599 * will also not lock the PTEs for the pte_entry() callback. This is useful for 600 * walking kernel pages tables or page tables for firmware. 601 * 602 * Note: Be careful to walk the kernel pages tables, the caller may be need to 603 * take other effective approaches (mmap lock may be insufficient) to prevent 604 * the intermediate kernel page tables belonging to the specified address range 605 * from being freed (e.g. memory hot-remove). 606 */ 607 int walk_kernel_page_table_range(unsigned long start, unsigned long end, 608 const struct mm_walk_ops *ops, pgd_t *pgd, void *private) 609 { 610 /* 611 * Kernel intermediate page tables are usually not freed, so the mmap 612 * read lock is sufficient. But there are some exceptions. 613 * E.g. memory hot-remove. In which case, the mmap lock is insufficient 614 * to prevent the intermediate kernel pages tables belonging to the 615 * specified address range from being freed. The caller should take 616 * other actions to prevent this race. 617 */ 618 mmap_assert_locked(&init_mm); 619 620 return walk_kernel_page_table_range_lockless(start, end, ops, pgd, 621 private); 622 } 623 624 /* 625 * Use this function to walk the kernel page tables locklessly. It should be 626 * guaranteed that the caller has exclusive access over the range they are 627 * operating on - that there should be no concurrent access, for example, 628 * changing permissions for vmalloc objects. 629 */ 630 int walk_kernel_page_table_range_lockless(unsigned long start, unsigned long end, 631 const struct mm_walk_ops *ops, pgd_t *pgd, void *private) 632 { 633 struct mm_walk walk = { 634 .ops = ops, 635 .mm = &init_mm, 636 .pgd = pgd, 637 .private = private, 638 .no_vma = true 639 }; 640 641 if (start >= end) 642 return -EINVAL; 643 if (!check_ops_safe(ops)) 644 return -EINVAL; 645 646 return walk_pgd_range(start, end, &walk); 647 } 648 649 /** 650 * walk_page_range_debug - walk a range of pagetables not backed by a vma 651 * @mm: mm_struct representing the target process of page table walk 652 * @start: start address of the virtual address range 653 * @end: end address of the virtual address range 654 * @ops: operation to call during the walk 655 * @pgd: pgd to walk if different from mm->pgd 656 * @private: private data for callbacks' usage 657 * 658 * Similar to walk_page_range() but can walk any page tables even if they are 659 * not backed by VMAs. Because 'unusual' entries may be walked this function 660 * will also not lock the PTEs for the pte_entry() callback. 661 * 662 * This is for debugging purposes ONLY. 663 */ 664 int walk_page_range_debug(struct mm_struct *mm, unsigned long start, 665 unsigned long end, const struct mm_walk_ops *ops, 666 pgd_t *pgd, void *private) 667 { 668 struct mm_walk walk = { 669 .ops = ops, 670 .mm = mm, 671 .pgd = pgd, 672 .private = private, 673 .no_vma = true 674 }; 675 676 /* For convenience, we allow traversal of kernel mappings. */ 677 if (mm == &init_mm) 678 return walk_kernel_page_table_range(start, end, ops, 679 pgd, private); 680 if (start >= end || !walk.mm) 681 return -EINVAL; 682 if (!check_ops_safe(ops)) 683 return -EINVAL; 684 685 /* 686 * The mmap lock protects the page walker from changes to the page 687 * tables during the walk. However a read lock is insufficient to 688 * protect those areas which don't have a VMA as munmap() detaches 689 * the VMAs before downgrading to a read lock and actually tearing 690 * down PTEs/page tables. In which case, the mmap write lock should 691 * be held. 692 */ 693 mmap_assert_write_locked(mm); 694 695 return walk_pgd_range(start, end, &walk); 696 } 697 698 int walk_page_range_vma_unsafe(struct vm_area_struct *vma, unsigned long start, 699 unsigned long end, const struct mm_walk_ops *ops, void *private) 700 { 701 struct mm_walk walk = { 702 .ops = ops, 703 .mm = vma->vm_mm, 704 .vma = vma, 705 .private = private, 706 }; 707 708 if (start >= end || !walk.mm) 709 return -EINVAL; 710 if (start < vma->vm_start || end > vma->vm_end) 711 return -EINVAL; 712 713 process_mm_walk_lock(walk.mm, ops->walk_lock); 714 process_vma_walk_lock(vma, ops->walk_lock); 715 return __walk_page_range(start, end, &walk); 716 } 717 718 int walk_page_range_vma(struct vm_area_struct *vma, unsigned long start, 719 unsigned long end, const struct mm_walk_ops *ops, 720 void *private) 721 { 722 if (!check_ops_safe(ops)) 723 return -EINVAL; 724 725 return walk_page_range_vma_unsafe(vma, start, end, ops, private); 726 } 727 728 int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops, 729 void *private) 730 { 731 struct mm_walk walk = { 732 .ops = ops, 733 .mm = vma->vm_mm, 734 .vma = vma, 735 .private = private, 736 }; 737 738 if (!walk.mm) 739 return -EINVAL; 740 if (!check_ops_safe(ops)) 741 return -EINVAL; 742 743 process_mm_walk_lock(walk.mm, ops->walk_lock); 744 process_vma_walk_lock(vma, ops->walk_lock); 745 return __walk_page_range(vma->vm_start, vma->vm_end, &walk); 746 } 747 748 /** 749 * walk_page_mapping - walk all memory areas mapped into a struct address_space. 750 * @mapping: Pointer to the struct address_space 751 * @first_index: First page offset in the address_space 752 * @nr: Number of incremental page offsets to cover 753 * @ops: operation to call during the walk 754 * @private: private data for callbacks' usage 755 * 756 * This function walks all memory areas mapped into a struct address_space. 757 * The walk is limited to only the given page-size index range, but if 758 * the index boundaries cross a huge page-table entry, that entry will be 759 * included. 760 * 761 * Also see walk_page_range() for additional information. 762 * 763 * Locking: 764 * This function can't require that the struct mm_struct::mmap_lock is held, 765 * since @mapping may be mapped by multiple processes. Instead 766 * @mapping->i_mmap_rwsem must be held. This might have implications in the 767 * callbacks, and it's up tho the caller to ensure that the 768 * struct mm_struct::mmap_lock is not needed. 769 * 770 * Also this means that a caller can't rely on the struct 771 * vm_area_struct::vm_flags to be constant across a call, 772 * except for immutable flags. Callers requiring this shouldn't use 773 * this function. 774 * 775 * Return: 0 on success, negative error code on failure, positive number on 776 * caller defined premature termination. 777 */ 778 int walk_page_mapping(struct address_space *mapping, pgoff_t first_index, 779 pgoff_t nr, const struct mm_walk_ops *ops, 780 void *private) 781 { 782 struct mm_walk walk = { 783 .ops = ops, 784 .private = private, 785 }; 786 struct vm_area_struct *vma; 787 pgoff_t vba, vea, cba, cea; 788 unsigned long start_addr, end_addr; 789 int err = 0; 790 791 if (!check_ops_safe(ops)) 792 return -EINVAL; 793 794 lockdep_assert_held(&mapping->i_mmap_rwsem); 795 vma_interval_tree_foreach(vma, &mapping->i_mmap, first_index, 796 first_index + nr - 1) { 797 /* Clip to the vma */ 798 vba = vma->vm_pgoff; 799 vea = vba + vma_pages(vma); 800 cba = first_index; 801 cba = max(cba, vba); 802 cea = first_index + nr; 803 cea = min(cea, vea); 804 805 start_addr = ((cba - vba) << PAGE_SHIFT) + vma->vm_start; 806 end_addr = ((cea - vba) << PAGE_SHIFT) + vma->vm_start; 807 if (start_addr >= end_addr) 808 continue; 809 810 walk.vma = vma; 811 walk.mm = vma->vm_mm; 812 813 err = walk_page_test(vma->vm_start, vma->vm_end, &walk); 814 if (err > 0) { 815 err = 0; 816 break; 817 } else if (err < 0) 818 break; 819 820 err = __walk_page_range(start_addr, end_addr, &walk); 821 if (err) 822 break; 823 } 824 825 return err; 826 } 827 828 /** 829 * folio_walk_start - walk the page tables to a folio 830 * @fw: filled with information on success. 831 * @vma: the VMA. 832 * @addr: the virtual address to use for the page table walk. 833 * @flags: flags modifying which folios to walk to. 834 * 835 * Walk the page tables using @addr in a given @vma to a mapped folio and 836 * return the folio, making sure that the page table entry referenced by 837 * @addr cannot change until folio_walk_end() was called. 838 * 839 * As default, this function returns only folios that are not special (e.g., not 840 * the zeropage) and never returns folios that are supposed to be ignored by the 841 * VM as documented by vm_normal_page(). If requested, zeropages will be 842 * returned as well. 843 * 844 * As default, this function only considers present page table entries. 845 * If requested, it will also consider migration entries. 846 * 847 * If this function returns NULL it might either indicate "there is nothing" or 848 * "there is nothing suitable". 849 * 850 * On success, @fw is filled and the function returns the folio while the PTL 851 * is still held and folio_walk_end() must be called to clean up, 852 * releasing any held locks. The returned folio must *not* be used after the 853 * call to folio_walk_end(), unless a short-term folio reference is taken before 854 * that call. 855 * 856 * @fw->page will correspond to the page that is effectively referenced by 857 * @addr. However, for migration entries and shared zeropages @fw->page is 858 * set to NULL. Note that large folios might be mapped by multiple page table 859 * entries, and this function will always only lookup a single entry as 860 * specified by @addr, which might or might not cover more than a single page of 861 * the returned folio. 862 * 863 * This function must *not* be used as a naive replacement for 864 * get_user_pages() / pin_user_pages(), especially not to perform DMA or 865 * to carelessly modify page content. This function may *only* be used to grab 866 * short-term folio references, never to grab long-term folio references. 867 * 868 * Using the page table entry pointers in @fw for reading or modifying the 869 * entry should be avoided where possible: however, there might be valid 870 * use cases. 871 * 872 * WARNING: Modifying page table entries in hugetlb VMAs requires a lot of care. 873 * For example, PMD page table sharing might require prior unsharing. Also, 874 * logical hugetlb entries might span multiple physical page table entries, 875 * which *must* be modified in a single operation (set_huge_pte_at(), 876 * huge_ptep_set_*, ...). Note that the page table entry stored in @fw might 877 * not correspond to the first physical entry of a logical hugetlb entry. 878 * 879 * The mmap lock must be held in read mode. 880 * 881 * Return: folio pointer on success, otherwise NULL. 882 */ 883 struct folio *folio_walk_start(struct folio_walk *fw, 884 struct vm_area_struct *vma, unsigned long addr, 885 folio_walk_flags_t flags) 886 { 887 unsigned long entry_size; 888 bool expose_page = true; 889 struct page *page; 890 pud_t *pudp, pud; 891 pmd_t *pmdp, pmd; 892 pte_t *ptep, pte; 893 spinlock_t *ptl; 894 pgd_t *pgdp; 895 p4d_t *p4dp; 896 897 mmap_assert_locked(vma->vm_mm); 898 vma_pgtable_walk_begin(vma); 899 900 if (WARN_ON_ONCE(addr < vma->vm_start || addr >= vma->vm_end)) 901 goto not_found; 902 903 pgdp = pgd_offset(vma->vm_mm, addr); 904 if (pgd_none_or_clear_bad(pgdp)) 905 goto not_found; 906 907 p4dp = p4d_offset(pgdp, addr); 908 if (p4d_none_or_clear_bad(p4dp)) 909 goto not_found; 910 911 pudp = pud_offset(p4dp, addr); 912 pud = pudp_get(pudp); 913 if (pud_none(pud)) 914 goto not_found; 915 if (IS_ENABLED(CONFIG_PGTABLE_HAS_HUGE_LEAVES) && 916 (!pud_present(pud) || pud_leaf(pud))) { 917 ptl = pud_lock(vma->vm_mm, pudp); 918 pud = pudp_get(pudp); 919 920 entry_size = PUD_SIZE; 921 fw->level = FW_LEVEL_PUD; 922 fw->pudp = pudp; 923 fw->pud = pud; 924 925 if (pud_none(pud)) { 926 spin_unlock(ptl); 927 goto not_found; 928 } else if (pud_present(pud) && !pud_leaf(pud)) { 929 spin_unlock(ptl); 930 goto pmd_table; 931 } else if (pud_present(pud)) { 932 page = vm_normal_page_pud(vma, addr, pud); 933 if (page) 934 goto found; 935 } 936 /* 937 * TODO: FW_MIGRATION support for PUD migration entries 938 * once there are relevant users. 939 */ 940 spin_unlock(ptl); 941 goto not_found; 942 } 943 944 pmd_table: 945 VM_WARN_ON_ONCE(!pud_present(pud) || pud_leaf(pud)); 946 pmdp = pmd_offset(pudp, addr); 947 pmd = pmdp_get_lockless(pmdp); 948 if (pmd_none(pmd)) 949 goto not_found; 950 if (IS_ENABLED(CONFIG_PGTABLE_HAS_HUGE_LEAVES) && 951 (!pmd_present(pmd) || pmd_leaf(pmd))) { 952 ptl = pmd_lock(vma->vm_mm, pmdp); 953 pmd = pmdp_get(pmdp); 954 955 entry_size = PMD_SIZE; 956 fw->level = FW_LEVEL_PMD; 957 fw->pmdp = pmdp; 958 fw->pmd = pmd; 959 960 if (pmd_none(pmd)) { 961 spin_unlock(ptl); 962 goto not_found; 963 } else if (pmd_present(pmd) && !pmd_leaf(pmd)) { 964 spin_unlock(ptl); 965 goto pte_table; 966 } else if (pmd_present(pmd)) { 967 page = vm_normal_page_pmd(vma, addr, pmd); 968 if (page) { 969 goto found; 970 } else if ((flags & FW_ZEROPAGE) && 971 is_huge_zero_pmd(pmd)) { 972 page = pfn_to_page(pmd_pfn(pmd)); 973 expose_page = false; 974 goto found; 975 } 976 } else if ((flags & FW_MIGRATION) && 977 pmd_is_migration_entry(pmd)) { 978 const softleaf_t entry = softleaf_from_pmd(pmd); 979 980 page = softleaf_to_page(entry); 981 expose_page = false; 982 goto found; 983 } 984 spin_unlock(ptl); 985 goto not_found; 986 } 987 988 pte_table: 989 VM_WARN_ON_ONCE(!pmd_present(pmd) || pmd_leaf(pmd)); 990 ptep = pte_offset_map_lock(vma->vm_mm, pmdp, addr, &ptl); 991 if (!ptep) 992 goto not_found; 993 pte = ptep_get(ptep); 994 995 entry_size = PAGE_SIZE; 996 fw->level = FW_LEVEL_PTE; 997 fw->ptep = ptep; 998 fw->pte = pte; 999 1000 if (pte_present(pte)) { 1001 page = vm_normal_page(vma, addr, pte); 1002 if (page) 1003 goto found; 1004 if ((flags & FW_ZEROPAGE) && 1005 is_zero_pfn(pte_pfn(pte))) { 1006 page = pfn_to_page(pte_pfn(pte)); 1007 expose_page = false; 1008 goto found; 1009 } 1010 } else if (!pte_none(pte)) { 1011 const softleaf_t entry = softleaf_from_pte(pte); 1012 1013 if ((flags & FW_MIGRATION) && softleaf_is_migration(entry)) { 1014 page = softleaf_to_page(entry); 1015 expose_page = false; 1016 goto found; 1017 } 1018 } 1019 pte_unmap_unlock(ptep, ptl); 1020 not_found: 1021 vma_pgtable_walk_end(vma); 1022 return NULL; 1023 found: 1024 if (expose_page) 1025 /* Note: Offset from the mapped page, not the folio start. */ 1026 fw->page = page + ((addr & (entry_size - 1)) >> PAGE_SHIFT); 1027 else 1028 fw->page = NULL; 1029 fw->ptl = ptl; 1030 return page_folio(page); 1031 } 1032